1834, "fact or condition of being relative" (apparently coined by Coleridge, of God, in "Notes on Waterland's Vindication of Christ's Divinity"), from relative, adj. + -ity. In scientific use, connected to the theory of Albert Einstein (1879-1955), published 1905 (special theory of relativity) and 1915 (general theory of relativity), but the word was used in roughly this sense by J.C. Maxwell in 1876.